SEASIDE, Calif. >> A teacher in Northern California accidentally fired his gun inside a classroom, injuring three students, police said.

Dennis Alexander, who is also a reserve police officer, was pointing the gun at the ceiling to make sure it was not loaded when the weapon discharged Tuesday inside his classroom at Seaside High School in the coastal community of Seaside, KSBW-TV reported.

The Seaside Police Department said no one suffered “serious injuries.” One 17-year-old boy sustained moderate injuries when bullet fragments lodged in his neck, the student’s father, Fermin Gonzales, told KSBW.

“It’s the craziest thing. It could have been very bad,” Gonzales said.

Alexander was teaching a gun safety lesson for his administration of justice and was about to show the students how to disarm someone, Gonzales said.

Gonzales said no officials contacted parents to let them know what happened and that he was shocked when his son returned home with blood on his shirt and bullet fragments in his neck. He rushed his son to a hospital for X-rays.

“I’m just pretty upset that no one told us anything and we had to call the police ourselves to report it,” Gonzales said.

Alexander was placed on administrative leave from his teaching job and he was also placed on administrative leave at the Sand City Police Department, police and schools officials said.

Monterey Peninsula Unified School District sent a letter to parents saying its human resources department, the high school administrators and the Seaside Police Department “immediately began investigating the incident, including interviewing students in the class.”

It said counseling was made available to students and that it could not release any other details “due to the nature of this personnel incident.”